Generally, expensive goods such as sound equipment are put into a casing and then are covered with a cover. Thereafter, the casing and the cover are locked by a locking device. In such a locked state, it is possible to safely store and convey the expensive goods.
The locking device of the casing and the cover was disclosed in Europe Patent No. 1,840,307, which pertains to a locking device for a transport box.
According to the previously registered patent, in the state where a shell is secured to each of the casing and the cover, as a handle rotates forwards, a tilting guide and a locking hook are moved forwards, and simultaneously, a cam moves up along a curved surface, so that they maintain an inclined state by a protruding height of the curved surface.
In this case, the tilting guide is pressed by a lead spring that is secured to a housing, so that the removal of the tilting guide is prevented.
Further, after the contact of side ends of respective shells, as the handle rotates backwards, the cam moves down along the curved surface, so that the tilting guide and the locking hook are moved downwards, and simultaneously, the locking hook is moved rearwards while being coupled to a space of the locking housing. Thereby, the locking hook is caught by the space to be locked thereto, thus maintaining a locked state of the casing and the cover.
In the previously registered patent, the lead spring pressing an end of the tilting guide downwards is secured to the housing with a rivet. However, this is problematic in that a working process of securing the lead spring to the housing with the rivet is complicated, and in addition, a frictional force between the tilting guide and the lead spring is excessively generated when the handle is rotated in the state where a front end of the lead spring comes into close contact with the tilting guide, so that the rotation of the handle and the forward and rearward movement of the locking hook are not smoothly performed, thus causing inconvenience.
Further, it is problematic in that the handle should be rotated 180 degrees or more to allow the cam to be moved up and down along the curved surface, so that a larger force is required, and thereby it is inconvenient to use and friction noise and abrasion may undesirably occur due to a point contact between the cam and the curved surface.
Furthermore, the curved surface is formed to protrude from the shell in a conical shape. However, it is problematic in that a working process for precisely forming the curved surface is difficult, causes defective forming, and increases manufacturing cost due to a waste of raw materials resulting from the defective forming.